John Bulter and Dov Friedman of Foreign Affairs discuss the roots of Fethullah Gülen’s power in Turkey and the mounting evidence linking him to July’s failed coup attempt. Washington should be prepared to allow Gülen to be brought to justice in Turkey, they argue, and the Gülen Movement’s schools, business, and political relationships in the US warrant thorough investigation.

Few dispute the Gulen Movement’s efforts to enter the military power structure from the 1980s onward. Nokta magazine—a publication staunchly aligned with Kemalism, the secularist founding ideology of the Turkish state—published an exposé of Gulenists’ inroads into the military in 1986. “Grit your teeth and hide yourselves until you are staff officers,” it quoted an older Gulenist telling teenage military students in his charge. “Pray [only] with your eyes. By the 2000s, Turkey will be in our grasp.”

Ever fearful of Gulenist motivations and capabilities, a group of senior military officers targeted in the fabricated Sledgehammer investigations began compiling a secret list of fellow officers they felt certain had Gulenist sympathies. This list, of which Foreign Affairs has obtained a copy, is not comprehensive: it contains no names from the air force, for example, where the list’s compilers likely had no sources. It also surely excludes many officers who successfully hid their allegiances from their colleagues. Critically though, the list does provide essential corroborating evidence for claims that Gulenists orchestrated the failed coup.

Gulen’s influence is cause for genuine concern. His followers have established charter school networks implicated—at the very least—in racketeering, bid-rigging, and possible H-1B visa violations. They have built cozy political relationships with everyone from local school boards all the way to Capitol Hill—with indications of financial improprieties along the way.

A refusal to extradite Gulen would shock many in Turkey and would intensify already hysterical anti-Americanism in pro-AKP media outlets—fueling speculation of tectonic shifts in the alliance. Yet, betting on such an outcome would be unwise. Turkey has worked to repair strained international relationships in a revised, post-activist foreign policy. That effort warmed relations with Russia and Israel, and it anticipates stable pragmatic ties with the United States. It is fair to wonder, though, about the corrosive effects of Turkey’s anti-American, anti-Western posture. A 70-year relationship is far more valuable than the use of essentially fungible military bases. Turkey should not overrate the strength of its position while recognizing what it still has: a long-standing, institutional relationship with the United States it would do well to preserve.